Dynamics Of Trace Elements In Alpine Meadow On Eastern Qinghai-tibetan Plateau

The alpine meadow on eastern Qinghai-Tibetan Plateau were selected and designed 4 treatments( continuous grazing, reseeding and sward ripping, fertilizing and non-grazing) to measure the contents of trace elements(Fe, Mn, Zn and Cu in soil and Ca, Mg, Fe, Mn, Zn and Cu in forage) in order to analyze the dynamic and supply amount of those trace elements, and their relationships. The main research results are as follows:1. The contents of trace elements in soil changed with season. The contents of Fe and Mg in soil varied with a same pattern. And the contents of total Fe and Mg in soil reached the highest in July while the contents of available Fe and Mn the lowest. The contents of total Zn and Cu in soil were the highest in May, and the contents of available Zn and Cu were the highest in July.2. The contents of Zn and Cu in soil were low. The content of total Zn in soil ranged from 8.83 to 16.39 mg/kg within 5 months, and it was far below the average value in China. The content of available Zn varied from 85.6 to 181.39 ug/kg, which was extremely deficient. The total content of Cu in soil varied from 5.83 to 8.56 mg/kg, and the content of available Cu in soil varied from 1.75 to 3.49 ug/kg, which were lower than the threshhold value.3. The contents of Fe and Mn in soil were increased in reseeding and fertilizing treatments, but the content of Zn and Cu was not obviously increased. The content of trace elements in non-grazing treatment was less than those in continuous grazing treatment.4. The contents of Ca, Mg, Fe, Mn, Zn and Cu in forage showed an obvious seasonal variation and they reached the highest in May. The contents of Mg and Ca in forage dropped to the lowest in September, while the rest 4 elements had the lowest contents in July and August, and the highest in September.5. The contents of Mg, Fe, Mn and Zn in forage could meet the demand of grazing livestock. However, the Ca content could meet the demand only from May to July and it was deficient in August and September. The Cu content in forage was seriously deficient and varied from 0.16 to 4.10 mg/kg.6. The contents of 6 trace elements in forage negatively correlated with the aboveground biomass and they decreased along with the increase of aboveground biomass. As to the relationships between trace element contents in soil and forage, only the Zn content in grazing treatment, and Mn and Fe in non-grazing treatment, the correlation was significant.7. The contents of Ca, Mg, Fe and Cu in forage were increased in treatments of sward ripping fertilizing and non-grazing. The Mn content in forage was higher than other treatments. The Zn content in forage was decreased in fertilizing treatment.